Leaked video of Republican nominee Mitt Romney at closed-door fundraisers show him saying that "no matter what" he does, 47 percent of the population is going to vote for Obama because they are "are dependent upon government." Tonight in California, Romney did not back down from what he had said.

The video clips, which were posted by Mother Jones, show Romney telling donors that 47 percent of voters will chose Obama "no matter what" because they are people "who are dependent upon government, who believe that they are victims, who believe the government has a responsibility to care for them, who believe that they are entitled to health care, to food, to housing, to you-name-it. That that's an entitlement. And the government should give it to them. And they will vote for this president no matter what…These are people who pay no income tax."

"My job is not to worry about those people," Romney says in the video. "I'll never convince them they should take personal responsibility and care for their lives."

Portions of the video were posted anonymously on YouTube in June while longer, but still incomplete, versions were posted on Monday by Mother Jones, which claims it "has confirmed its authenticity." ABC News has not thus far been able independently to validate the authenticity of the clips.

Mother Jones reported that the event took place on May 17 at the Boca Raton, Fla., home of private equity manager Marc Leder.

Responding to the leaked video on Monday night at a press conference in Costa Mesa, Calif., Romney stood by what he said in the clip, but he admitted he could have been more eloquent at the time the video was shot.

Romney said that he was speaking "off the cuff" in response to a question.

"It's a question and answer, as I recall, about the process of the campaign and how I'm going to get the 51 or 52 percent I need, and I point out it's by focusing on those folks that are neither in [Obama's] camp nor in my camp," Romney said.

"I recognize that among those that pay no tax, approximately 47 percent of Americans, I'm not likely to be highly successful with the message of lowering taxes. That's not as attractive to those who don't pay income taxes as it is to those who do," Romney said. "And likewise those who are reliant on government are not as attracted to my message of slimming down the size of government. And so I then focus on those individuals who I believe are most likely to be able to be pulled into my camp and help me win the 51 or 50.1 percent that I need to become the next President."

Earlier on Monday, the Obama campaign responded swiftly and harshly to the video.

"It's shocking that a candidate for President of the United States would go behind closed doors and declare to a group of wealthy donors that half the American people view themselves as 'victims,' entitled to handouts, and are unwilling to take 'personal responsibility' for their lives," Jim Messina, Obama for America campaign manager, said in a statement. "It's hard to serve as president for all Americans when you've disdainfully written off half the nation."

The tapes are, as Mother Jones reports, from fundraisers "which occurred after Romney had clinched the Republican presidential nomination," although it is not specified when or where the fundraiser was. The clips have been edited into 38-second to one-and-a-half minute chunks.

In the series of leaked videos, Romney also tells supporters that if he "had he been born of Mexican parents I'd have a better shot of winning this," that he "was born with a silver spoon, which is the greatest gift you can have: which is to get born in America," and that he "inherited nothing" from his wealthy father.

"My dad and Ann's dad did quite well in their lives, but when they came to the end of their lives and passed along the inheritances to Ann and to me, we both decided to give it all away," Romney says. "So I have inherited nothing. Everything Ann and I have we have earned the old fashioned way."

Romney explains to the campaign donors that he has not been harsher in his attacks against President Obama because he is trying to win over people who voted for Obama in 2008.

"And because they voted for him, they don't want to be told that they were wrong, that he's a bad guy, that he did bad things, that he's corrupt," Romney says. "Those people that we have to get, they want to believe they did the right thing, but he just wasn't up to the task."

On the economy, Romney said the markets would react favorably if he won the White House on November 6.

"We'll see - without actually doing anything - we'll actually get a boost in the economy," he says, admitting two sentences later that he "can never predict what the markets will do. Sometimes it does the exact opposite of what I would have expected."

And while the Republican candidate's campaign said today that he would start offering more specifics about his policies, Romney said during this fundraiser that "in a setting like this, a highly intellectual subject - discussion on a whole series of important topics typically doesn't win elections."

Romney lets press into some parts of his fundraisers that are held at public venues. Often, reporters are allowed for one part of a three-part event. When fundraisers are held at private homes, the press is barred altogether. The types of question-and-answer sessions that are captured in these videos are generally closed to the press.

President Obama similarly does not allow press to sit in on question-and-answer sessions. The Romney campaign announced earlier today, before Mother Jones posted the videos, that cameras would now be allowed into fundraisers at public venues.

In the YouTube video, posted under the username "Romney Exposed," the GOP candidate recalls going to China "to buy a factory there," which he describes as having "a huge fence with barbed wire and guard towers" and where "young women between the ages of 18 and 22 or 23? worked long hours and earned a "pittance."